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Alkylthio)chloroacetylenes 1 react with thiosemicarbazones 2 at room temperature in a medium of aliphatic ketone to form hydrochlorides of 2-alkanone-N-[4-(organylthio)-1,3-thiazol-2-yl]hydrazones 3 in yields of up to 65%.Although poorly understood so far, the reactions of (organylthio)chloroacetylenes 1 with S,N-multinucleophiles provide a potential source of new classes of polyfunctional unsaturated compounds, including heteroatomic ones. Moreover, from a fundamental viewpoint, these present an essential source of information on some features on the nucleophilic substitution of a halogen at the triple bond in the presence of some competing nucleophilic centers during attack at a hetero-conjugated system uniting the atoms of two sp-carbons, sulfur and chlorine.It is known that (alkylthio)chloroacetylenes react with 2-aminoethane-1-thiol to form 2-{[2-(alkylthio)ethynyl]-thio}ethane-1-ammonium chlorides, 1 whereas with thiourea they give S-(alkylthioethynyl)isothiuronium chlorides and N-[1-(alkylthio)ethynylidene]thiourea. 2 Under comparable conditions the reaction of (phenylthio)chloroacetylene with thiourea leads to 4-(phenylthio)-1,3-thiazol-2(3H)-imine hydrochloride in quantitative yield. 2The reaction of haloacetylenes with thiosemicarbazones has not been studied until the present work. It has been briefly reported that bromoethynyl(organyl)ketones with thiosemicarbazine and its 1-and 4-organyl-substituted compounds form 1,3,4-thiazole derivatives. 3 The polydentate nature of thiosemicarbazones as nucleophiles (with due account taken of their tautomeric forms) suggests that during their interaction with (organylthio)chloroacetylenes diverse heterocycles can be formed. Therefore, we have first carried out and studied the reaction of (organylthio)chloroacetylenes 1 with dialkylketone thiosemicarbazones 2 in order to extend our knowledge of the reactivity and synthetic potential of the heteroconjugated S-CºC-Cl system and to synthesize novel heterocyclic polyfunctional compounds. Taking into consideration the multidentate character of the latter as well as the presence of three electrophilic centers (halogen atom and two sp-carbons) in the molecule of halogenacetylenes 1, the result of interaction of the above reagents was far from predictable.(Alkylthio)chloroacetylenes 1a,b react with thiosemicarbazones 2a-c at 20-22°C in a medium of the same aliphatic ketone to form in a chemo-and regioselective manner hydrochlorides of 2-alkanone-N-[4-(organylthio)-1,3-thiazol-2-yl]hydrazones 3a-c in 51-65% yield (Scheme 1).The thiazoles 3a-c are crystalline substances, very soluble in water, ethanol, dimethylsulfoxide, poorly soluble in chloroform and insoluble in ether. The salt nature of these compounds is confirmed by mercurometric titration: only one equivalent of ion-chloride per mole of the compound is fixed. The IR spectra of compounds 3a-c show a broad Scheme 1Downloaded by: Simon Fraser University Library. Copyrighted material.

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